Continuity mistake: In the park, Sarah begins reciting the lines, "Through dangers untold...beyond the Goblin City..." and her hair in back is pulled up very loosely in her barrette, seen clearly as she speaks. Yet in the shot of her back, when Merlin barks, her hair is twisted perfectly in the barrette. (00:03:20)
Continuity mistake: As Sarah starts to run down the labyrinth, just after she's entered it, the ribbons on the back of her jacket go from tied to loose then to tied again. (00:18:45)
Continuity mistake: When Sarah is putting lipstick on, the newspaper clippings and photos on her mirror change position and arrangement between different angles and shots. (00:06:05)
Visible crew/equipment: When Hoggle jumps off the wall's ledge onto the gate's metallic robot, the lines attached to Hoggle are visible. Hoggle then yells, "Get out of there!" to the controller of the giant robot. As he leaps on top of him, and when Hoggle says, "My turn now," the lines attached to Hoggle are seen again. (01:16:50)
Other mistake: When Sarah is in the room with the old hag who lives at the rubbish dump, the old hag asks, "What's the matter, dearie? Don't you like your toys?" Connelly is mouthing the hag's lines, presumably as a prompt to recall her own lines. (01:10:45)
Visible crew/equipment: A cannonball goes flying, when Sarah and the gang are at the Goblin City (The one that says "I hit something? Yes? No?") and as it heads towards the wall, you can see the wire it's attached to. (01:18:30)
Continuity mistake: When Sarah shows Hoggle her plastic bracelet in the oubliette, when trying to get him to take her as far as he can to the centre of the labyrinth, in one shot she holds the bracelet between her finger and thumb, then in the next shot it is dangling off her finger. (00:31:05)
Continuity mistake: This can only been seen in the letterbox version of Labyrinth. After Sarah says, "It's all junk," the garbage lady grabs a ballerina music box and says, "Well what about this, this is not junk," and hands it to Sarah. She takes it, then for a second it cuts back to the garbage lady. The music box is still sitting on the table after it was handed to Sarah. (01:13:45)
Visible crew/equipment: In Goblin City, a small boulder jumps into the mouth of a cannon just as a guard yells, "Fire!" After exploding, the guard then says, "Hey, I just fired you," as the "cannonball" hops around near the cannon yelling, "Ouch, ouch, ouch!" and the wires attached to it are visible. (01:25:30)
Deliberate mistake: When Sarah, et al are surrounded by the Goblins in Goblin City, the first cannon fires causing an explosion in front of some buildings, one of which has a hanging sign with scissors on it. Later, after the squatty Goblin says, "Hey! I just fired you!" another cannon fires causing an explosion, and the very same shot is shown, only the first one was flipped. (01:20:15 - 01:25:35)
Continuity mistake: When Jareth's shadow menacingly appears on the rug beside the crib, Sarah's legs face the doorway on the rug - which has light stripes parallel to the doorway. However, in the close-up of Sarah's legs, when the snake/scarf turns into a Goblin, her legs face the doorway and the rug stripes run perpendicularly. (00:11:50)
Revealing mistake: When Sarah discovers Toby has gone from his cot, Goblins start moving about in her fathers room. The second goblin we see laughs, and jumps down from the top of her fathers four poster bed. As the goblin does this, you can see the shadow of a boom mic bob down onto the material that drapes from each poster of the bed. (00:11:05)
Revealing mistake: At Jareth's castle, in the room with the Escher stairs, Sarah sees Toby and she jumps. It's very apparent that it's a stuntwoman jumping from the ledge in the wide shot. (01:30:20)
Continuity mistake: When Sarah walks into the darkened bedroom, in the shots facing the double back doors the hanging light fixture over the crib, the mobile, and picture beside it are all visible. When Jareth appears, in the first shot facing him, the mobile hangs lower (note the archway), the picture is closer to the floral trim around the archway; and solely for Jareth's dramatic entrance, the light fixture is gone - though it should easily be visible in this shot, and the crib is now at an angle. (00:10:25 - 00:11:55)
Continuity mistake: When the Goblins are spooking Sarah in the dark bedroom, she spins round as a few pop out at the same time (near the vanity table, from the dresser drawer...), and one lifts the lid of a brown case atop the tall dresser. However, in the previous shots of the well lit room and when she first entered the dark bedroom, that case was gone - replaced with flowers. (00:08:35 - 00:11:35)
Continuity mistake: In the junkyard, after Ludo pulls Sarah out of the garbage room, Sir Didymus says "M'lady look, we're almost there...." and then there is a shot of the gates to the Goblin City. The junk which sits around the gates to the Goblin City is piled rather low. However when Sarah, Ludo and Sir Didymus arrive at the gates, the junk to the right hand side of the gates is now piled up much, much higher. (01:11:30)
Continuity mistake: When Sarah is hanging on the branch over the bog, Ludo calls a rock and the rock rolls into the bog, and is pretty round, with no large flat areas on it. However when it's floating in the bog, Sarah jumps onto it and the rock now has a very large flat area. (00:58:45)
Continuity mistake: As Sir Didymus bangs the large grey brick holding the bridge up and says "Have no fear sweet maiden...", the large brick then suddenly falls. Between shots the amount of green fungus and moss covering the grey brick increases. (00:58:10)
Continuity mistake: As Hoggle and Sarah fall out the end of the chute that leads to the Bog of Eternal Stench, look closer and you can see that Sarah falls through the end of the chute twice. (00:52:45)
Continuity mistake: Sarah is rescued from her fake house and head towards the gates to the Goblin City. Hoggle is seen poking his head out in the wide shot and then a close-up. The things around Hoggle change in the two shots. (01:14:25)
Answer: Sarah did indeed select the right door and did ask a sensible, albeit confusing question. The reason she fell into the oubliette (and the helping hands) is because as she walked through the door she said "I think I'm getting smarter. This is a piece of cake" - saying "piece of cake" within the Labyrinth to say how easy something is brings bad luck upon those who say it. Sarah said it to Jareth and he upped the stakes (reducing her time). Hoggle said it later (in Goblin City) and then they got surrounded by Goblins.